clippy_lints/src/formatting.rs

   1 use crate::utils::{differing_macro_contexts, snippet_opt, span_help_and_lint, span_note_and_lint};
   2 use if_chain::if_chain;
   3 use rustc::declare_lint_pass;
   4 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintPass};
   5 use rustc_session::declare_tool_lint;
   6 use syntax::ast::*;
   7
   8 declare_clippy_lint! {
   9     /// **What it does:** Checks for use of the non-existent `=*`, `=!` and `=-`
  10     /// operators.
  11     ///
  12     /// **Why is this bad?** This is either a typo of `*=`, `!=` or `-=` or
  13     /// confusing.
  14     ///
  15     /// **Known problems:** None.
  16     ///
  17     /// **Example:**
  18     /// ```rust,ignore
  19     /// a =- 42; // confusing, should it be `a -= 42` or `a = -42`?
  20     /// ```
  21     pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
  22     style,
  23     "suspicious formatting of `*=`, `-=` or `!=`"
  24 }
  25
  26 declare_clippy_lint! {
  27     /// **What it does:** Checks the formatting of a unary operator on the right hand side
  28     /// of a binary operator. It lints if there is no space between the binary and unary operators,
  29     /// but there is a space between the unary and its operand.
  30     ///
  31     /// **Why is this bad?** This is either a typo in the binary operator or confusing.
  32     ///
  33     /// **Known problems:** None.
  34     ///
  35     /// **Example:**
  36     /// ```rust,ignore
  37     /// if foo <- 30 { // this should be `foo < -30` but looks like a different operator
  38     /// }
  39     ///
  40     /// if foo &&! bar { // this should be `foo && !bar` but looks like a different operator
  41     /// }
  42     /// ```
  43     pub SUSPICIOUS_UNARY_OP_FORMATTING,
  44     style,
  45     "suspicious formatting of unary `-` or `!` on the RHS of a BinOp"
  46 }
  47
  48 declare_clippy_lint! {
  49     /// **What it does:** Checks for formatting of `else`. It lints if the `else`
  50     /// is followed immediately by a newline or the `else` seems to be missing.
  51     ///
  52     /// **Why is this bad?** This is probably some refactoring remnant, even if the
  53     /// code is correct, it might look confusing.
  54     ///
  55     /// **Known problems:** None.
  56     ///
  57     /// **Example:**
  58     /// ```rust,ignore
  59     /// if foo {
  60     /// } { // looks like an `else` is missing here
  61     /// }
  62     ///
  63     /// if foo {
  64     /// } if bar { // looks like an `else` is missing here
  65     /// }
  66     ///
  67     /// if foo {
  68     /// } else
  69     ///
  70     /// { // this is the `else` block of the previous `if`, but should it be?
  71     /// }
  72     ///
  73     /// if foo {
  74     /// } else
  75     ///
  76     /// if bar { // this is the `else` block of the previous `if`, but should it be?
  77     /// }
  78     /// ```
  79     pub SUSPICIOUS_ELSE_FORMATTING,
  80     style,
  81     "suspicious formatting of `else`"
  82 }
  83
  84 declare_clippy_lint! {
  85     /// **What it does:** Checks for possible missing comma in an array. It lints if
  86     /// an array element is a binary operator expression and it lies on two lines.
  87     ///
  88     /// **Why is this bad?** This could lead to unexpected results.
  89     ///
  90     /// **Known problems:** None.
  91     ///
  92     /// **Example:**
  93     /// ```rust,ignore
  94     /// let a = &[
  95     ///     -1, -2, -3 // <= no comma here
  96     ///     -4, -5, -6
  97     /// ];
  98     /// ```
  99     pub POSSIBLE_MISSING_COMMA,
 100     correctness,
 101     "possible missing comma in array"
 102 }
 103
 104 declare_lint_pass!(Formatting => [
 105     SUSPICIOUS_ASSIGNMENT_FORMATTING,
 106     SUSPICIOUS_UNARY_OP_FORMATTING,
 107     SUSPICIOUS_ELSE_FORMATTING,
 108     POSSIBLE_MISSING_COMMA
 109 ]);
 110
 111 impl EarlyLintPass for Formatting {
 112     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
 113         for w in block.stmts.windows(2) {
 114             match (&w[0].kind, &w[1].kind) {
 115                 (&StmtKind::Expr(ref first), &StmtKind::Expr(ref second))
 116                 | (&StmtKind::Expr(ref first), &StmtKind::Semi(ref second)) => {
 117                     check_missing_else(cx, first, second);
 118                 },
 119                 _ => (),
 120             }
 121         }
 122     }
 123
 124     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
 125         check_assign(cx, expr);
 126         check_unop(cx, expr);
 127         check_else(cx, expr);
 128         check_array(cx, expr);
 129     }
 130 }
 131
 132 /// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
 133 fn check_assign(cx: &EarlyContext<'_>, expr: &Expr) {
 134     if let ExprKind::Assign(ref lhs, ref rhs, _) = expr.kind {
 135         if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion() {
 136             let eq_span = lhs.span.between(rhs.span);
 137             if let ExprKind::Unary(op, ref sub_rhs) = rhs.kind {
 138                 if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
 139                     let op = UnOp::to_string(op);
 140                     let eqop_span = lhs.span.between(sub_rhs.span);
 141                     if eq_snippet.ends_with('=') {
 142                         span_note_and_lint(
 143                             cx,
 144                             SUSPICIOUS_ASSIGNMENT_FORMATTING,
 145                             eqop_span,
 146                             &format!(
 147                                 "this looks like you are trying to use `.. {op}= ..`, but you \
 148                                  really are doing `.. = ({op} ..)`",
 149                                 op = op
 150                             ),
 151                             eqop_span,
 152                             &format!("to remove this lint, use either `{op}=` or `= {op}`", op = op),
 153                         );
 154                     }
 155                 }
 156             }
 157         }
 158     }
 159 }
 160
 161 /// Implementation of the `SUSPICIOUS_UNARY_OP_FORMATTING` lint.
 162 fn check_unop(cx: &EarlyContext<'_>, expr: &Expr) {
 163     if_chain! {
 164         if let ExprKind::Binary(ref binop, ref lhs, ref rhs) = expr.kind;
 165         if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion();
 166         // span between BinOp LHS and RHS
 167         let binop_span = lhs.span.between(rhs.span);
 168         // if RHS is a UnOp
 169         if let ExprKind::Unary(op, ref un_rhs) = rhs.kind;
 170         // from UnOp operator to UnOp operand
 171         let unop_operand_span = rhs.span.until(un_rhs.span);
 172         if let Some(binop_snippet) = snippet_opt(cx, binop_span);
 173         if let Some(unop_operand_snippet) = snippet_opt(cx, unop_operand_span);
 174         let binop_str = BinOpKind::to_string(&binop.node);
 175         // no space after BinOp operator and space after UnOp operator
 176         if binop_snippet.ends_with(binop_str) && unop_operand_snippet.ends_with(' ');
 177         then {
 178             let unop_str = UnOp::to_string(op);
 179             let eqop_span = lhs.span.between(un_rhs.span);
 180             span_help_and_lint(
 181                 cx,
 182                 SUSPICIOUS_UNARY_OP_FORMATTING,
 183                 eqop_span,
 184                 &format!(
 185                     "by not having a space between `{binop}` and `{unop}` it looks like \
 186                      `{binop}{unop}` is a single operator",
 187                     binop = binop_str,
 188                     unop = unop_str
 189                 ),
 190                 &format!(
 191                     "put a space between `{binop}` and `{unop}` and remove the space after `{unop}`",
 192                     binop = binop_str,
 193                     unop = unop_str
 194                 ),
 195             );
 196         }
 197     }
 198 }
 199
 200 /// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else`.
 201 fn check_else(cx: &EarlyContext<'_>, expr: &Expr) {
 202     if_chain! {
 203         if let ExprKind::If(_, then, Some(else_)) = &expr.kind;
 204         if is_block(else_) || is_if(else_);
 205         if !differing_macro_contexts(then.span, else_.span);
 206         if !then.span.from_expansion() && !in_external_macro(cx.sess, expr.span);
 207
 208         // workaround for rust-lang/rust#43081
 209         if expr.span.lo().0 != 0 && expr.span.hi().0 != 0;
 210
 211         // this will be a span from the closing ‘}’ of the “then” block (excluding) to
 212         // the “if” of the “else if” block (excluding)
 213         let else_span = then.span.between(else_.span);
 214
 215         // the snippet should look like " else \n    " with maybe comments anywhere
 216         // it’s bad when there is a ‘\n’ after the “else”
 217         if let Some(else_snippet) = snippet_opt(cx, else_span);
 218         if let Some(else_pos) = else_snippet.find("else");
 219         if else_snippet[else_pos..].contains('\n');
 220         let else_desc = if is_if(else_) { "if" } else { "{..}" };
 221
 222         then {
 223             span_note_and_lint(
 224                 cx,
 225                 SUSPICIOUS_ELSE_FORMATTING,
 226                 else_span,
 227                 &format!("this is an `else {}` but the formatting might hide it", else_desc),
 228                 else_span,
 229                 &format!(
 230                     "to remove this lint, remove the `else` or remove the new line between \
 231                      `else` and `{}`",
 232                     else_desc,
 233                 ),
 234             );
 235         }
 236     }
 237 }
 238
 239 #[must_use]
 240 fn has_unary_equivalent(bin_op: BinOpKind) -> bool {
 241     // &, *, -
 242     bin_op == BinOpKind::And || bin_op == BinOpKind::Mul || bin_op == BinOpKind::Sub
 243 }
 244
 245 /// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
 246 fn check_array(cx: &EarlyContext<'_>, expr: &Expr) {
 247     if let ExprKind::Array(ref array) = expr.kind {
 248         for element in array {
 249             if let ExprKind::Binary(ref op, ref lhs, _) = element.kind {
 250                 if has_unary_equivalent(op.node) && !differing_macro_contexts(lhs.span, op.span) {
 251                     let space_span = lhs.span.between(op.span);
 252                     if let Some(space_snippet) = snippet_opt(cx, space_span) {
 253                         let lint_span = lhs.span.with_lo(lhs.span.hi());
 254                         if space_snippet.contains('\n') {
 255                             span_note_and_lint(
 256                                 cx,
 257                                 POSSIBLE_MISSING_COMMA,
 258                                 lint_span,
 259                                 "possibly missing a comma here",
 260                                 lint_span,
 261                                 "to remove this lint, add a comma or write the expr in a single line",
 262                             );
 263                         }
 264                     }
 265                 }
 266             }
 267         }
 268     }
 269 }
 270
 271 fn check_missing_else(cx: &EarlyContext<'_>, first: &Expr, second: &Expr) {
 272     if !differing_macro_contexts(first.span, second.span)
 273         && !first.span.from_expansion()
 274         && is_if(first)
 275         && (is_block(second) || is_if(second))
 276     {
 277         // where the else would be
 278         let else_span = first.span.between(second.span);
 279
 280         if let Some(else_snippet) = snippet_opt(cx, else_span) {
 281             if !else_snippet.contains('\n') {
 282                 let (looks_like, next_thing) = if is_if(second) {
 283                     ("an `else if`", "the second `if`")
 284                 } else {
 285                     ("an `else {..}`", "the next block")
 286                 };
 287
 288                 span_note_and_lint(
 289                     cx,
 290                     SUSPICIOUS_ELSE_FORMATTING,
 291                     else_span,
 292                     &format!("this looks like {} but the `else` is missing", looks_like),
 293                     else_span,
 294                     &format!(
 295                         "to remove this lint, add the missing `else` or add a new line before {}",
 296                         next_thing,
 297                     ),
 298                 );
 299             }
 300         }
 301     }
 302 }
 303
 304 fn is_block(expr: &Expr) -> bool {
 305     if let ExprKind::Block(..) = expr.kind {
 306         true
 307     } else {
 308         false
 309     }
 310 }
 311
 312 /// Check if the expression is an `if` or `if let`
 313 fn is_if(expr: &Expr) -> bool {
 314     if let ExprKind::If(..) = expr.kind {
 315         true
 316     } else {
 317         false
 318     }
 319 }